The bag itself.
While you may opt for a jacket with many big pockets, this may not be very practical.
The most basic bag is a strong sack, better than nothing and with the addition of some basic rope you have a way to close it and attach it to your back to carry it.
It’s worth knowing about this basic improvisation because for some it will be all there is. it should be noted that the sack could have two straps instead of one.
The next step up is a simple small day pack, similar you what school students might have. the advantages will be: more solid fabric, more comfortable straps, larger comfortable load, additional compartment for smaller items and to keep things more ordered.
the deluxe solution is a sport/hiking day pack where the additional features are: Even more compartments, very comfortable straps and the likely addition of a water bladder compartment. Adding a water bladder will allow you to carefully control your hydration which will keep you more comfortable for longer.
If you require a longer journey a larger hiking backpack will be what you need , it will essentially be an even larger version of the hiking day pack, and obviously allow you to carry a larger weight and volume of things.